Launcher: a grid of icons, with badges; the list stays as a Setting

The Launcher shows the Apps as a 4 x 3 grid of 32 x 32 icons, the
selected one's name under it (issue #9). The icons are the website's
own, doubled, and two drawn the same way for SSH and the Shell; they
are PNGs in assets/icons, turned into arrays by scripts/make_icons.py,
which CI checks. The selected tile is the website's: dark blue on cyan,
with notched corners.

- GridModel (lib/ui, host-tested) holds the selection and the scrolling.
- App::badge(): a dot on the tile for unread IRC messages, a Track
  recording, a Capture running, an SSH session open.
- Settings > Launcher: Grid or List.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

lib/ui/src/grid_model.h

@@ -0,0 +1,33 @@
+#pragma once
+
+namespace roro {
+
+// Selection and scrolling for a grid of `cols` columns showing `visibleRows` rows at a time, filled
+// row by row. Left and Right go through every item and wrap around; Up and Down stay in the
+// column and wrap around, landing on the last item where the last row has no such column.
+class GridModel {
+   public:
+    GridModel(int cols, int visibleRows) : cols_(cols), rows_(visibleRows) {}
+
+    void setCount(int count);
+    int count() const { return count_; }
+    int selected() const { return selected_; }  // -1 when empty
+    int cols() const { return cols_; }
+    int rows() const { return count_ ? (count_ - 1) / cols_ + 1 : 0; }
+    int firstVisibleRow() const { return first_; }
+    int visibleRows() const { return rows_; }
+
+    void select(int index);
+    void left();
+    void right();
+    void up();
+    void down();
+
+   private:
+    int cols_, rows_;
+    int count_ = 0;
+    int selected_ = -1;
+    int first_ = 0;
+};
+
+}  // namespace roro